Description of the Prior Art and Problems Therein
One-package, RTV, silicone elastomer compositions are in wide use as sealants, coatings, and adhesives for application to substrates, machinery, and devices in a number of sectors, such as the construction and civil engineering sectors and electrical and electronic sectors. The use of these one-package, RTV, silicone elastomer compositions involves their storage in a sealed container, such as a tube or cartridge; then, at the actual point of application, extrusion of the silicone elastomer composition as a paste; and thereafter finishing the surface to smoothness using, for example, a spatula. Thus, the surface of the composition must not cure for the particular period of time elapsing from extrusion into the atmosphere until finishing. Moreover, even when the surface has begun to cure, additional time is required for the curing region to develop adequate mechanical strength, and deformation of the composition by outside forces is problematic during the time interval extending from cure initiation at the surface until the development of mechanical strength. In specific terms, when subjected to a stretching or elongational deformation, the curing region will rupture due to its inadequate mechanical strength. This occurrence of rupture in one location can lead to fracture of the entire body after its cure due to stress concentration at the aforesaid rupture site.
The occurrence of rupture during the course of curing can be prevented by increasing the cure rate of subject silicone elastomer compositions, but simply increasing the cure rate functions to shorten the working time available for spatula finishing. The use of this approach is also associated with a ready tendency for the silicone elastomer composition to yellow during storage. It is therefore desirable to develop a one-package, RTV, silicone elastomer composition that exhibits an acceptable working time and still rapidly develops mechanical strength once curing has started.